Hi myhang. That was such a kind gift for your aunt to have given you! The requirements to unlock a T-Mobile device can be found here - Unlock your mobile wireless device. If your aunt was the former owner of this T-Mobile iPhone and meets those eligibility requirements, she'd simply need to Contact Us and provide the IMEI so that we can reference the previous usage on her account to verify that eligibility and we'll be happy to submit the request for her!
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